The number of persons exhibiting diabetes or impaired glucose tolerance which would be diabetes, has increased in recent years due to Westernization of the diet, a lack of exercise resulting from the development of transportation facilities and the like. In particular, diabetes causes complications including diabetic neuropathies such as numbness and pain, cataracts, diabetic retinopathy, arteriosclerosis, diabetic nephropathy or diabetic gangrene, and there are also cases that ultimately lead to death. Accordingly, the treatment thereof can be said to be extremely important.
Although improvement of lifestyle is desired for the prevention or treatment of diabetes, this cannot always be easily achieved.
In addition, although the treatment for diabetes involves methods for regulating the level of insulin in the blood by an insulin injection or an oral administration of hypoglycemic agents, these methods are accompanied by adverse side effects, while a diet therapy and an exercise therapy have the problems of being difficult for a patient to comply with them.
Amidst these circumstances, attempts have been made to prevent or treat diabetes and hyperglycemia by using natural ingredients which have a wide range of actions and no potential for adverse side effects and the like even if taken for a long period. For example, Patent Document 1 describes a therapeutic and preventive agent for hyperglycemia containing an extract of a plant belonging to the genus Bidens, Patent Document 2 describes a composition for improving hyperglycemia having as an active ingredient a dried acetic acid fermented product of the Amaranthus seed, Patent Document 3 describes a preventive and/or therapeutic agent for a diabetic disease containing as an active ingredient Sargassum horneri or a treated product thereof, Patent Document 4 describes a fucoidan-based health food which suppresses hyperglycemia and maintains blood sugar at a low level, and Patent Document 5 describes a food for persons with hyperglycemia containing olive leaves or an extract thereof.
On the other hand, with respect to acacia, acacia honey is known, and tannin which is extracted from bark thereof is known to be able to be used as a tanning agent or a wood adhesive, while more recently, extracts of genus Acacia have been disclosed to have selective inhibitory effects on COX-2 (Patent Document 6), and bark of genus Acacia has been disclosed to have active oxygen eliminating effects (Patent Document 7) and skin whitening effects due to the effect of inhibiting tyrosinase activity (Patent Document 8). However, acacia bark and polyphenols derived from acacia bark have heretofore not been known to have a hypoglycemic action.
[Patent Document 1] JP2004-323362A
[Patent Document 2] JP7-138178A
[Patent Document 3] JP2004-217559A
[Patent Document 4] JP2004-24054A
[Patent Document 5] JP2002-10753A
[Patent Document 6] JP2004-532811A
[Patent Document 7] JP2004-352639A
[Patent Document 8] JP10-025238A